Superheterodyne radio receiver employing a multifunction tube



E. D. PHINNEY ET AL SUPERHETERODYNE RADIO RECEIVER EMPLOYING AMULTIFUNCTION TUBE May 20, 1952 5 Sheets-Sheet 1 Filed Sept. 21, 1946DEA/I Y NETWORK INVENTORS EDWARD 0. Pfl/N/VEY 41150 H. REEVES May 20, 1E. D. PHlNNEY ET AL SUPERHETERODYNE RADIO RECEIVER EMPLOYING AMULTIFUNCTION TUBE s Shets-Sheet 2 Fild Sept. 21, 1946 INVENTORS {OW/1RDD. P/vl/V/VEY WW my wm 1% MN 4156' H. FfEI ES ATTORNEY $5 Hu X WNQQPatented May 20, 1952 SUPERHETERODYNE RADIO RECEIVEREM- PLOYING AMULTIFUNCTION TUBE Edward D. Phinney, Mount Vernon, N. Y., and AlecHarley Reeves, Reigate, England, assignors to International StandardElectric Corporation, New York, N. Y., a corporation of DelawareApplication September 21, 1946, Serial No. 698,484

15 Claims. 1

This invention relates to electrical Wave translation circuits andpertains more particularly to radio amplifiers and radio receivers.

Radio circuits have been known for some time in whichone vacuum tube ora series of tubes performs simultaneously a plurality of functions, suchas amplifying and detecting a wave of a single frequency or amplifyingat the same time several waves of different frequencies. Examples ofsuch circuits are the well known regenerative and reflex circuits.

' An object of the invention is to perform two or more operations in asingle device successively and repeatedly in a simple, economic andefficient manner.

- Another object is to produce a radio circuit wherein, a translationdevice such as a vacuum tube or a group of vacuum tubes and theirassociated circuits, carries out a plurality of separate operations orfunctions successively whereby the number of circuit elements requiredis greatly reduced. For example, one vacuum tube performs successivelyat a high rate of speed several different operations that ordinarilywould be performed simultaneously by several different tubes. Theseoperations may include amplifying high or intermediate frequencies,detecting, and amplifying audio frequencies.

. Another object is to reduce the number of tubes required for a radioreceiver.

Another object is to increase the amplification of a given amplifiercircuit.

Another object is to detect or mix and/or amplifyelectrical waves in asingle electron discharge device successively and repeatedly at a superaudible rate.

Further, objects of this invention will appear I in the descriptionwhich follows. a In carrying out these various functions successivelyadvantage istakenof the pulse transmission principle according to which,as is well known. a wave of any frequency maybe reproduced by selectinga plurality of spaced points or sections, i. e. pulses of the wave,amplifying, or otherwise treating the pulses, and thencreating fromtheresulting pulses a signal wave." In the audio frequency range thesounds may satisfactorilyreproduced from pulses representing threepoints per cycle of the highest frequency it is desired to reproduce. Y

.Thus, this invention involves a circuit comprising a single translatingdevice throughwhich a selected pulse or portion of a signalmay berecycledat least once, successively and non-currently, from the outputofthedevice through a delay network to the input of said device wherebysaid pulse may be translated and withdrawn; and then repeating saidoperation (preferably at a comparatively high rate), with a newlyselected pulse. By recycling is to be understood the feeding of theoutput signal from the translating device back to the input thereof,whereby said translating device is enabled further to act on the saidoutput signal.

A better understanding of the above objects and features of thisinvention may be had by referring to the following detailed descriptionand accompanying drawings of specific embodiments in which:

Figure 1 is a schematic wiring diagram of an amplifier circuit embodyingthis invention;

Figure 2 is a graph of waveforms useful in explaining the operation ofthe circuit in Figure 1;

Figure 3 is a schematic wiring diagram of a radio receiver circuitembodying this invention, and

Figure 4 is a graph of waveforms useful in explaining the operation ofthe circuit in Figure 3.

Referring to Fig. 1, I is a triode containing output transformer 2connected to a high tension power supply or B+ battery 3. The secondarywinding of 2 is connected through delay network 4 to the gridtransformer 5. The grid circuit is completed through windings oftransformers 5 and I3, and is connected to the oathode through resistor6 shunted by condenser 1. Condenser 8 enables a local control wave 9(shown in Fig. 2) to be applied to the grid of tube I from terminal I0.

If the circuit is to be used as ahigh frequency amplifier, the signalinput wave H (shown in Fig. 2) may be introduced at antenna ,l2 coupledto the grid transformer I 3. Transformers 2, 5 and I3 and also delaynetwork 4 are arranged to pass the desired signal high'frequency, as isalso the output winding l4 coupled to transformer 2 and connected tooutput terminals l5.

Assume first, in order to describe the operation of this circuit, thatthe input signal wave It consists of successive trains of high frequencyoscillations such as l6 and I1, which will be ,on" from to to 151, offfrom h to tv, and then on again from tv to ta, etc. The control wave 9is applied at terminal I!) simultaneously with the input signal wave attime to, and the control wave becomes suddenly, positive, making thevalve l conductive as a class A amplifier. Conductivity lasts until timeis whichis slightly in excess of timeti. After:the'lsmalllgapltz to isthus the same as I6, but has the voltage increased by the amplificationfactor of .the valve I under the given conditions, i. e. from VI to V2.The time constant of delay network 4 is arranged to be equal to the timeto to is. Thus, if delay network 4 has no attenuation, the am.-

plitude V2 of IQ will appear at the grid of valve I during the time t3to 134. In this way it will be amplified again by the factor of valve Igiving an output wave 2I of voltage V3.

Now the valve I is not conductive again until time 157, at which timethe second wave train 2! of voltage V3 has completely passed throughdelay network 4 and died away. At the instant t7 therefore, the onlyvoltage at the grid of valve I will be the second train I'I of thesignal wave II, which will appear'in the output of the amplifier as thevoltage V2 of portion 22 and will last until time is, whereupon it is,returned to the grid" of valve I through the delay network 4 for furtheramplification as explained hereinafter in conjunction with signal inputor train it.

Voltage1V3 therefore will be equivalent to two stages of amplificationof the valve I. This twice amplified voltage may be extracted atterminals I5 either alone. or together with the smaller voltage V2, asdesired.

It is. not necessary for the signal input wave II itselfltoxbepulsed asshown so long as this input is present'between the times is and t4, t7and; ta, etc. If it, is continuous the only effect will be a slightincrease in the voltage V3 with outv aifecting the stability of thecircuit.

If, the delay "network 4 is terminated perfectly by transformers 2' and5, there will be no reflections. .If, however, the termination isimperfect and; there is a reflection component of N db (decibels)returning to the transformer 2 after the .time 154, the circuit will beunstable for an amplification factor of valve I greater than terval'between is and it must be greater than three or more periods, each,equal to the delay timeof the. network 4." If, for example, it. isslightly greater than three times the delay or time constant of network4, it will only be the second reflectionand not the. first which cancause, instability. This second reflection in general can be, arrangedto be considerably more db down than thelamplification factor of valveI. (Alternatively, if time ta to t7=5 times the delay of network 4,,thefsecond reflection too will be cut off by valve I.) In' the case justexplained the timeta to t must be /5j0f the time to to ii. The averageamplified; energy in the output circuit is thus:

where .e is the inputamplitude and A is the energy amplification perstage. If, for example, A=l000, this) comes to approximately 200,000which is approximately 200 times that of an ordi nary single stageamplifier.

If desired, the same principle can be used for a larger effective numberof amplifications than two, all in the same tube I.

If the circuit comprising 2, 4 and 5 has the characteristics of a filter(e. g. band-pass filter) at the signal frequency, the over-all frequencycharacteristic will be that of M stages of such a filter, if theamplification is carried out M times. The signal frequency, of course,must be such that one period of it is small compared to the time delayof the network 4, and the pass band of the transformers and delaynetwork must be wide enough to pass the pulsed envelope of the signal.

i. e. wave 9 in Figurez.

The application of the above circuit in a superheterodyne'receiver isshown in Fig. 3, wherein the valve 23 performs all the functions of ahigh frequency amplifier, mixer, three stages of I. F.

amplification, and a second detector. Valve 24 is the beatingoscillator. The low frequency amplifier stage is shown as the separatevalve 25 (but this also may be combined'with the functions of 23 if thefull average output of 23 is not required). Tube or valve '24 may be atriode oscillator operating by means of transformer 26, of which theprimary winding 21 is shunted by condenser 28. The anode circuit iscompleted through pulse transformer 29 at which the high frequencycomponent is shunted by condenser 30, and then connected to a hightension power source or B+ battery 3 I. By means of battery 32-,connected through transformer 33 and resistor 34 (shunted by condenser35), a negative bias is applied to tube 24 sufiicient to prevent itsoscillation. The constants are arranged so that if a positive pulse-isapplied externally to the grid of tube 24 (e. g. by means of the key 36.battery 31 and secondary winding 38 of transformer 33) the circuit willgive a short train of oscillations 39 (see Fig. 4) at thebeatingoscillator frequency, irrespective of the duration of the appliedpositive pulse which occurs at the time no (Fig. 4). Resistance 34 andcondenser 35, so chosen as to constitute, in conjunction-with highfrequency transformer'26, a blocking or squiggin circuit of a type wellknown inthe art, will cause a negative charge to accumulate on the gridby grid current, sufiicient to quench the oscillation after apredetermined very short timeinterval. say, at in. By suitable choice oftheconstants of transformer 29, and of the'input impedance of delaynetwork section 40, such'a single train of oscillations is arranged tocause a single positive pulse in the secondary of transformer 29ofduration substantially equal to that of the train of high frequencyoscillations 39. This pulse is due to the change in plate current of24'when oscillating, and condenser 30- prevents the high frequencycomponents from reaching 29. Transformer 29 is connected to six equalsections 40, 4|, 42, 43, 44 and 45 of a delay network passing the mainpulse components. Onarrival; at the output of delay device 45 ofthe-network, which is terminated by resistor 46 and condenser 41, theoutput positive pulse isapplied through decoupling resistance 48 back tothe grid of 24 through line 49 andthe secondary of transformer 26. Whenthe pulse strikes the grid of tube 24. the voltage resulting'is arrangedto be sufficient to cause another train of oscillations 50" (see Fig; 4)similar to 39, thus causing a second pulse at 29 which will again passthrough the delay devices or network 40 through 45. Thesequence ofeventswill thus be; repeated indefinitely; the oscillatorbeing operativefor a shortperiod tm to 2512 in each cycle followed by a period ofquiescence from tm to tag (see Fig. 4). The circuit constants may bechosen so that each oscillator train lasts for a time tm to in, slightlyshorter than the delay time ho to in or 1213 tons, etc. of each of thedelay sections 40 through 45.

The grid circuit of valve 23 is completed through resistor 5| antennainput transformer 52 (to antenna 53), transformer 54 and bias such asbattery 55 via resistor 56. The battery 55 and resistor 56 are shuntedby condenser 51, and the voltage of 5,5 is such that the plate currentof 23 is normally just cut off completely.

Starting from this condition, the key 36 is momentarily closed, andre-opened at time tm. The windings of transformer 33 are so poled thatthe starting transient voltage, generated in the secondary or gridwinding when closing key 36 allows current from battery 31 to flow inthe primary winding 38, merely makes the grid of tube 24 slightly morenegative, and the tube accordingly remains inactive. When the key is're-opened, however, the abrupt cessation of current flow in the primarywinding sets up in the secondary winding a transient voltage much largerthan the previous transient, and of reverse sense, making the grid oftube 24 sufficiently positive to enable the tube to start oscillating,trains of oscillations being generated as described in connection withFig. 1. Following the opening of the key at time 1510, therefore, tube24 delivers a train of oscillations 39, Fig. 4, together with a D. C.pulse at the input of delay device 40, this pulse being positive toground and resulting from the envelope of the train of oscillations 39.When this pulse arrives at the output of delay device 44, a certainfraction of the pulse energy will pass through line 58 and condenser 59to. the junction 69 between 56 and 54. Condenser 51 is a shunt for thehigh frequency components only and will not short circuit the positiveor D. C. pulse components to ground. There will thus bea suddenrise ofpotential of the grid of 23; This value is arranged to be justsuflicient to overcome the bias of 55 and cause 23 to be a class Aamplifier. If the input signal 6| (shown in Fig. 4) is present at thismoment at antenna 53, it will be amplified in tube 23, and the outputselected by. the tuned primary inductance of transformer 62 togetherwith condenser 63 is applied through delay device 64, across resistor5|, thus getting back to the grid of tube 23. Delay device 64 has a timedelay equal to tie to tiz, same as that of each device 40 through 45,and has frequency characteristics (e. g. bandpass) passing the desiredsignal high frequency components.

By the time signal 6| is amplified and is delayed (shown at 65 in Fig.4) and arrives back on to the grid of tube 23, the D. .0. pulse from theenvelope of 39 enabling this amplification to take place, will havepassed from the output of delay device 44 to the output of delay device45. At this moment, as explainedabove, valve 24 will give a burst ofoscillations 58 at the beating oscillation frequency, of durationslightly less than the delay time tza to 1531 of each of the devices 48through 45. By means of the extra winding 66 to transformer 26, some ofthis beating oscillator train is applied between the screen grid of tube23 and battery 61. This beating oscillator voltage on the screen isarranged to be sufiicient to overcome the bias of battery 55, enablingtube 23 to act as a-mixer'and detector during time in 00130;The;'resu1ting intermediate frequency 6 train 68 (in Fig. 4), offrequency such that a sufficient number of cycles of the intermediatefrequency are contained in the time corresponding to the delay in onesection of the delay devices 40 through 45, is applied throughtransformer 69 to delay device 10 (equal to that of each of the otherdelay devices) and from there through transformer 54 back to the grid oftube 23. (Condenser 1| is arranged to shunt the radio frequency signalcomponents only, and not the intermediate frequencies of 68. It can withadvantage be made to tune the secondary winding of transformer 54 to theintermediate frequency.)

By the time oscillations 68 arrive at transformer 54 and pass once moreon to the grid of tube 23, the beating oscillator 24 has ceased tofunction; but at this moment a positive D. C. pulse will appear at theoutput of delay device 40 and thence via the rectifier-resistorcombination 1213 and condenser 14, on to the junction 69. This positivepulse also is arranged to overcome the bias of battery 55, causing tube23 again to be a class A amplifier. The resulting amplified I. F. wave15 (Fig. 4) will again appear at 69 and once more be applied to delaydevice 19. This delay device 10 must have frequency characteristicspassing the I. F. components.

By the time that the amplified I. F. wave-15 has again reachedtransformer 54, the original D. C. pulse from 29 will have reached theoutput of delay device 4|. From device 4| a portion of this pulse energymay be similarly applied via rectifier-resistor combination 16-11 andcondenser 14 in such a way as again to cause a momentary reduction tozero of the negative bias of tube 23 producing further amplified I. F.wave 18 (see Fig. 4).

The operation described above occurs a third time, when the twiceamplified I. F. train 18 again reaches transformer 54 and when the D. C.pulses from 29 have reached the output of delay device 42. By means ofrectifier-resistor 19-80 a fraction of the pulse power is again appliedto condenser 14 and once more reduces the bias of tube 23 to produce astill further amplified I. F. wave 8| (see Fig. 4).

After three stages of amplification at the intermediate frequency (see15, 18 and 8|) in this way, the D. C. pulse from 29 will have reachedthe output of delay device 43. On this occasion a fraction of the D. C.pulse power is again applied via rectifier-resistor 8283, resistornetwork 84 and 85, and condenser 86 to the grid of tube 23. A tapping on84-85 produces a lower value of positive increase for the bias of tube23, but is sufficient to cause tube 23 to act as an anodebend seconddetector or rectifier to the thrice amplified I. F. train or wave 8|which then arrives at its grid. The resulting increase'o'f plate currentin tube 23 produces a D. 0. pulse 86' (see Fig. 4) in the secondarywinding of the low frequency transformer 81; condenser 88 shunting theI. F. This pulse 86' may then be passed via low pass filter 89 to thegrid of a low frequency amplifier tube 25; filter 89 passing the desiredaudio components only (see wave 90 in Fig. 4). The final audio outputmay be obtained via transformer 9| on terminals 92.

If desired, transformer 81 may be constructed to pass energy from eachwave (shown in Fig. 4) that passes from the anode of tube 23 or onlythat from the wave 86 by means of a suitable.

blocking circuit (not shown). Passage of energy from each wave may be ofadvantage when the I. F. gain at each successive amplification by tube 723 is small, in which.it;. is.of advantage to use for the seconddetection-the total amplified energy in the I. F. trains; and: notmerely the energy in the final output train.

One or more of the delay devices may be adjusted or varied at will tocause one or more of the recycled pulses to overlap with each otherintime, either wholly or partially, to vary the gain of the circuit. Ifdesired, the tube 23 may be biased so thatenergy'passes through it onlywhen two or more recycled sectionsor pulses. of energy overlapv in time.and add. to each other. Thus, by employing variable time-constantcircuits in one or more of the delay devices to vary the amount ofoverlap: of such pulses, a. variable gain control is obtained;

To ensure stability, it is necessary that certain of the above functionsofthe circuit'be' suppressed while the particular function desired atany moment is taking place. For this purpose, one diagonal of therectifier bridge 93 maybe connected across the input of delay device 64,and battery 94 connected across the other diagonal of the bridge viapulse transformer 95 to cause the bridge to short circuit the input todelay device 54 in the absence of voltage across transformer 95. Bymeans of a condenser 9.6,however, at the required moment in the sequencethat it is desired to passsignal through delay device 64, the pulse onthe output of'delay device 44 may be arranged to oppose throughout thewhole of its duration, the voltage of battery 94, thus opening thediagonal of the bridge 93 concerned, enabling signal 8| to pass todevice64. At all other moments the delay device 64 has' itsinput shortcircuited. Similarly, one diagonal of the rectifier bridge 9? may beconnected across the input of delay device iii, short circuitingthelatter due to the action of the battery 98, except at the desiredinterval for the operation of delay'device 1 0, i. e. at the moment ofarrival of D. C. pulses at the outputs of delay devices it, 4! or 42.

To prevent the pulsesv from. the various tappings on thedelaynetwork 40through 45 from getting back from one section to another, thus causingundesired interaction, the rectifiers 12, i6, '19, 82 and led areinserted and shunted respectively by resistances 13; TI, 80, 83'. andNH. Each rectifier-resistor combination thus has low resistance topositive pulses from the filter section to the desiredoutput point, buta hi h resistance in the reverse sense.

In addition to the provision of the stabilising bridges 93 and 91,further. protection may be secured by increasing the delay of delay.network M, preferably to an integral multiple of the delay of any one ofthe other sections. Thisfurther stabilisation may be necessary incertain cases to ensure that any undesired reflections around theintermediate frequency delay device ill have died away sufficientlybefore the next cycle of operations is commenced.

Thus, a superhetero-dyne receiver has been obtained wherein all theamplification and detection both at high and intermediate. frequenciesis due to a single device such as tube 23.

While the invention has been described in par.- ticular detail andpreferred forms illustrated, it is to be understood that it is notlimited thereto. It is further to be'understood that many othermodifications, adaptations, omissions; and additions may be made withoutdeparting from the scope of the invention as defined in the appendedclaims. In. particular, the inventionv may be adapted-to detection,amplification, frequency :1

8. changing and. other, such processing of signals other, than, speechmodulated signals, for example telegraph; teleprinter, facsimile, radar:and .the like signals, and alsoto frequency multiplying individing-systems 1 r a Whatisclaimedisr; r

l. A- radio translatorcomprising a single amplifier stage, means forrepeatedly amplifying a signal of a given-frequency in said stage, meansfor'varying theconditioning'of said stage'for'detectionv andamplification at a lower frequency. and means for repeatedly amplifying:said lower frequency signal in said stage.

2. A radio receiving circuit comprising an electron discharge tube,.a.source of local oscillations of a first frequency and means forsuccessively conditioning said tube. to perform separately: reception ofpulse waves of a second frequency, beating of said first'and secondfrequency to produce waves of a third frequency, amplification of saidwaves of said third frequency, and. detection of said waves of saidthird frequency.

3. A radio receiver comprising means for. receiving a radio frequencywave, an amplifying electron discharge tube, means to provide a pulse ofsaid received radio frequency at the input of said tube; meansforcoupling the output of said tube through a delay means to the inputwhereby said radio frequency pulse is amplified, means subsequentlyoperative forvarying the operating characteristics of said tube fordetection to produce a detected pulse, means for coupling, said detectedpulse from the output of said tube to its input through adelaymeanswhereby a repeated amplification of said detectedpulse'isobtained, means for subsequently producing an output signal pulse, andmeans for restoring the radio receiving means to its initial condition,wherebythe cycle of reception andoperation may be repeated.

4.. An amplifier circuit comprising an electron discharge tube, meansfor selecting and: separating from a signal wave time-spaced portionsthereof while rejecting intermediately timed portions, and means forrecyclingeach of said selected portions of said signal wave:through.said tube in a plurality of successive. time separated operations beforerepeating said recycling with a newly selected portion of. said signal.

5. An electric signalling apparatus comprising an input andoutputcircuit; a" feedback circuit coupling said input and output; circuits,means for applying a signal wave. tosaid input circuit, a translatingdevice coupled to said inputcircuit, and means for successivelyconditioning said translating device toperform, heterodyning andamplifying onsaid signa1 wave in a plurality of separate differentactions performed. successively at a super-audible. rate as said Wave.passes through said device.

61A system comprising a translatingv device, means for applying signalenergy to. said device, means for biasing said device topasssaidiener'gy therethrough while performing a given function thereon toalter the characteristics of. the passed energy, means for varying saidbias tones. the altered energy therethrough' While performing adifferent function onsaid altered energy to further'alter thecharacteristics thereof,.andmeans for controlling said devicecyclicallyto perform each of said functions at. least twice in;timespaced operations on said signal energy before performingthe nextfunction thereon:

'7. A' system according to claim 6 wherein said energy is. in the formof pulses: andsaidcontrolling means includesafeedback path between theoutput and input of said device, and delay means in said path having adelay value greater than the duration of each pulse.

8. A system according to claim 6 wherein said device is an amplifier.

9. A system according to claim 6 wherein said device is a singleelectron discharge tube.

10. A system according to claim 6 wherein the biasing means includesfurther including means for biassing said tube to operate as anamplifier, and means for varying the biassing of said tube to cause itto operate as a detector.

11. A radio circuit comprising an electron discharge device having aninput circuit and an output circuit, means for applying to said inputcircuit pulse modulated signals having a given repetition frequency, afeedback path from said output circuit to said input circuit, a delaydevice in said feedback path having a delay period greater than theduration of the pulses of said signals and means for causing saiddischarge device to operate successively and non-concurrently asamplifier and detector in the interval between the reception ofsuccessive signal pulses.

12. A radio circuit for reception of signals consisting of a series ofseparate pulses having a certain average recurrence rate comprising anelectron discharge device having an input circuit and an output circuit,a feedback path from said output circuit to said input circuit and meansfor causing said discharge device to act successively andnon-concurrently as amplifier and as detector in the interval betweenthe reception of one input pulse and the reception of the next inputpulse.

13. A radio circuit for reception of signals consisting of a series ofseparate pulses having a certain average recurrence rate comprising anelectron discharge device having an input circuit and an output circuit,a feedback path from said output circuit to said input circuit and meansfor causing said discharge device to act successively andnon-concurrently as amplifier, detector and amplifier in the intervalbetween the reception of one input pulse and the reception of the nextinput pulse.

14. A radio circuit comprising an electron discharge device having acontrol grid and an input circuit and an output circuit, means forapplying to said input circuit pulse modulated signals having a givenrepetition frequency, a feedback path from said output circuit to saidinput circuit, means for applying a biassing potential to said controlgrid to condition said device to perform different operations, and meansfor cyclically changing the said biassing potential to cause saiddischarge device to operate successively and nonconcurrently asamplifier and detector in the interval between the reception ofsuccessive signal pulses.

15. A radio circuit comprising an electron discharge device having aninput circuit and an output circuit, means for applying to said inputcircuit pulse modulated signals having a given repetition frequency, afeedback path from said output circuit to said input circuit, a delaydevice in said feedback path having a delay period greater than theduration of the pulses of said signals and means for causing saiddischarge device to operate successively and non-concurrently asoscillator and mixer in the interval between the reception of successivesignal pulses.

EDWARD D. PHINNEY. ALEC HARLEY REEVES.

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